Maybe Despair is 0.01%, but it's modified by resist so it only seems like 0.005%. This occured to me while playing Nasus, who's ulti is similar to this spell... the text told me I was doing 7% of my enemy's max hp per second, (because of my AP) but it sure didn't seem like it, and that Cho'gath managed to kill me anyway... :'(

Hmm hardly making sense to write anything exact right now, considering the tooltips probably are wrong... I've been making way too much damage with Q, and not enough with E when comparing it to the tooltip (+ E obviously even has the ap-bonus displayed wrong, I didn't feel like stealing 450% of their life per second...

But basically:
Mordekaiser

Passive: He has no Mana but a Shield-Bar... he passively is increasing an absorbing shield by 20% of his ability-damage. Shield has a Maximum of 150/300/450 and is decreasing by 5/10/15 per second

Q: Mace Of Spades
Deals bonus damage and his attack hits up to 3 additional targets, if the unit he hits is alone, his bonus damage is doubled

W:Creeping Death
Gives a buff to an Ally that improves his armor and MR and is dealing DPS to nearby enemies (and is quite buggy so you can kill allies atm, which evne gives you the money for their streak )

E: Siphon of Destruction (or something like that)
Cone-AoE-Skill that deals damage and additionally improves his passive shield per Unit that got hit by the skill

R: Um... Curse of the Buried something...
Is supposed to be stealing a percentage of the enemy HP (no idea whether max or current) over 12 secs. Additionally if the target dies while being cursed their spirit is enslaved and they're following Mordekaiser for 30 secs without being able to attack, but giving half of their life, attack damage and ability power to Mordekaiser.

Will give you the exact numbers and AP-Ratios (and names ) tomorrow, allthough I recall them to be something like Q: 0; W: 0.1 (over 8 seconds); E: 0.2; R: very very obviously wrong (60% of their current life per sec per 100 AP)

Q: Mace of Spades 0
W: Creeping Death 0.1 (time isn't in the description, but measured to the cooldown it appears to be 5 seconds... thus an 0.5 ratio alltogether)
E: Siphon of Destruction 0.25

R: Children of the Grave 0.1% per 100 AP (that sounds better than 60% per 100 AP )

Works slightly different now:
Curses an Enemy Champion for 8 seconds stealing 3%/3.5%/4% life per second.

If the Target dies while cursed their soul is enslaved and will follow the Mordekaiser for 30 seconds. During this time Mordekaiser gains one quarter of their ability power and attack damage. The Spirit gains 65%/75%/ of Mordekaisers adjusted damage, ability power and health totals.

On a sidenote: The description's saying that you can control pets by holding alt while right clicking... I just hope this will apply for all pets

Edit: forgot the scaling of children of the grave
And another Edit: forgot about the time of Creeping Death ^^

Q: Mace of Spades 0
W: Creeping Death 0.1 (time isn't in the description, but measured to the cooldown it appears to be 5 seconds... thus an 0.5 ratio alltogether)
E: Siphon of Destruction 0.25

R: Children of the Grave 0.1% per 100 AP (that sounds better than 60% per 100 AP )

Works slightly different now:
Curses an Enemy Champion for 8 seconds stealing 3%/3.5%/4% life per second.

If the Target dies while cursed their soul is enslaved and will follow the Mordekaiser for 30 seconds. During this time Mordekaiser gains one quarter of their ability power and attack damage. The Spirit gains 65%/75%/ of Mordekaisers adjusted damage, ability power and health totals.

On a sidenote: The description's saying that you can control pets by holding alt while right clicking... I just hope this will apply for all pets

Edit: forgot the scaling of children of the grave
And another Edit: forgot about the time of Creeping Death ^^

Thank you for these =)
this is a great help, it seems you've helped me more than any other person here